The present invention relates to testing systems, and more particularly, this invention relates to systems and methods for detecting electrostatic discharge (ESD) events in cabled devices.
In magnetic storage systems, data is commonly read from and written onto magnetic recording media utilizing magnetic transducers. Data is written on the magnetic recording media by moving a magnetic recording transducer to a position over the media where the data is to be stored. The magnetic recording transducer then generates a magnetic field, which encodes the data into the magnetic media. Data is read from the media by similarly positioning the magnetic read transducer and then sensing the magnetic field of the magnetic media. Some more common magnetic read transducers, such as magnetoresistive (MR) sensors, include anisotropic magnetoresistive (AMR), giant magnetoresistive (GMR), and tunnel valve magnetoresistive (TMR) sensors. Read and write operations may be independently synchronized with the movement of the media to ensure that the data can be read from and written to the desired location on the media.
Additionally, the manufacturing processes for many other devices, such as mobile telephones, laptop computers, handheld global positioning satellite (GPS) systems, any device using a semiconductor, etc., include steps where ESD events may cause damage to sensitive components of the devices. Many of these devices also include cabled components.
ESD is a major cost detractor in manufacturing facilities of MR heads, semiconductor devices, etc. The MR sensors are typically bonded to flexible cables to enable connection to external electronic devices, such as drives, controllers, etc. Similarly, components of mobile telephones and other semiconductor devices include sensitive elements bonded to cables, and sometimes to flexible cables. ESD events occur when currents pass through the MR sensor, or other sensitive components, which may occur due to various circumstances and from multiple sources. For example, ESD events may occur due to handling and use of MR sheet resistors with the build-up of electrostatic charges on the various components of a head or other objects which come into contact with the MR sensors and spontaneously discharge through the MR sensor leading to damage. Static charges may be externally produced and accumulate on instruments used by persons performing device manufacturing or testing functions. These static charges may also discharge through the devices, causing physical and/or magnetic damage to the sensors or other sensitive components.
Currently, engineers measure voltages of the cable or voltages of fixtures, testers, operators, etc., to determine whether there is a risk of ESD damage to the sensitive components of the electronic device. Conventional techniques used to determine risks make use of measurements external to the device to predict whether sufficiently high ESD currents might pass through the MR sensor or other sensitive components. These measurements external to the device are indirect measurements. Another approach that is currently used is to test the heads at various stages in the manufacturing process to determine if the heads are damaged. This also is an indirect measurement of the ESD event, as well as being a very expensive method (due to the cost of the ruined electronic devices once the damage is detected) which gives very little information as to the type, source, extent, etc., of the ESD event which caused the damage.